Vista - When shut down Vista, must disconnect the power supply and reconnect before booting

Thanks for the interest and help.
I have a dual boot system (Vista Enterprise and XP). I have built the computer myself and newly installed both OS. The computer works perfectly with XP. When I boot into Vista, everything works fine. Then when I shut down, I cannot boot the computer unless I disconnect the power supply and then reconnect the power supply. Then everything operates normally. If I boot into XP, then shut down, this does not happen...I can turn on the system and boot into either OS. All updates for both OS are current (SP1 for Vista and SP3 for XP). The system was a clean install. XP was installed first, then Vista. XP was installed directly to a SATA hard drive. Vista was installed to a separate RAID 1 SATA Hard Drive.
Any help would be appreciated.
Thanks

What do you mean when you say you cannot boot the computer? Does it boot up at all or fail during boot up?

This might be really wrong but I'm not sure how a dual-boot works exactly. However, you're using two hard-drives, is there a default hard-drive that you're computer boots up under? I know on my notebook, un-plugging the power supply and taking out the battery pack and putting it back in and re-connecting power supply power-cycles and restores default boot settings. I had issues booting up on my desktop too, I tried this and this helped.

I would be using one hard-drive for both operating systems and another hard-drive for the documents, photos, programs, videos etc

The symptoms you describe would seem to indicate a bad power supply. If possible, try using a different Power Supply Unit in your computer.

Also, try entering the system BIOS and resetting the power management settings to defaults.

You know...I've actually heard this one before, and it wasn't a faulty PSU since the system works fine until it's shutdown or using the XP Os instead. I believe it was XP the other user was using when this happened tho and it was a couple years back but reading this reminded me of it. I can't recall the fix tho, or even if they ever found it but I'll try searching tomorrow and see if I can find it on one of my other forums.\

Very weird issue indeed and I get the feeling this is being caused by an improper dual booting setup possibly corrupting the BIOS when the system changes and the unplug basically resets the BIOS defaults.

The sequence of installation of the OS, XP first and then Vista, means that whichever system you chose to boot into is on the "C" drive. For example if I decide to boot into XP, XP is on the "C" drive and Vista is the "D" drive. Vice versa if I choose to boot into Vista, Vista is the "C" drive and XP is the "D" drive. Don't ask me how I simply googled how to install a dual boot system and this is how it was said it was going to be.
The only thing I did differently was that I slipstreamed the SP1 into Vista prior to installation. I added SP3 after installation onto XP.

What I mean that I cannot boot the system is that if I shut down the computer in Vista, the OS shuts down as expected and the computer powers down. When I turn at a later time power up the system, the computer turns on but is in a similar state to hibernation. No beep, no going through the screens showing the hard drives, etc. when the system normally starts.

Conversely when I boot into XP, then shut down the system powers down. But I can power it up later and boot into either Vista or XP.

I'm afraid we need more details on how exactly you set up this dual boot system...
When you install more than one flavor of Windows it always writes certain files to the root directory of C:\ no matter what so it should be able to boot no matter what OS you are in at shutdown...
If however you disconnected the XP drive to install Vista then this did not happen and would explain the issue.
The only other way you would have this issue is if there is a faulty connection with the Vista drive...either power or the SATA connection itself.
Double-check all connections and post back with more details on how you set this up and we'll go from there.

I followed the following on a blank unformatted hard drive.

How To Dual Boot Windows XP And Vista - Make Tech Easier

My system:
XP (SP3)
VISTA (SP1)
MB: ASUSTeK Computer INC. Maximus II Formula
Processor: 2.50 gigahertz Intel Core2 Quad Q9300
Memory: 4 GB
Drives: 640 GB SATA partitioned into 50 GB (XP installed here) & 590 GB (uses for backup);
300 GB RAID 1 (Vista installed here)
1 TB external (backup)
Optical Drives: LG Bluray HL-DT-ST BDDVDRW GGC-H20L
Plextor PX-760A

Thanks.
When powering down and turningoff the computer and then at a later time booting, it almost seems when powering down from VIsta the computer will start in "hibernate" mode.
Thanks